1. Technical Field
The present disclosure relates to electronic circuits and more particularly to a filtering circuit with Bulk Acoustic Wave (BAW) resonators that can be digitally reconfigured.
2. Description of the Related Art
Today acoustic resonators are widespread in consumer applications but also in professional applications because of their high efficiency, including the realization of high performance band pass filters, and in particular in mobile telephony for the selection of transmission channels.
Research has been conducted on two types of acoustic resonators that show remarkable performance, namely the SAW resonators (Surface Acoustic Wave Resonator) and, more recently, the BAW (Bulk Acoustic Wave Resonator). In the first type, the acoustic resonator is located on the surface of a semiconductor product while in BAWs it lays inside a volume delimited between a lower electrode and a higher electrode so that the acoustic wave develops in this volume. BAW resonators are the subject of wide research from manufacturers of semi-conductor products because those components allow consideration of a high degree of integration of filtering circuits, thus allowing significant manufacturing costs savings.
BAW resonators allow higher frequencies than those used with SAWs, while achieving more compact structures.
Beyond the performance offered by BAW resonators for the realization of a digital filter, there is a need for easy configuration of filtering characteristics of a filter made of BAW resonators.
Such configuring has been achieved, so far, by using varactors connected in series or in parallel with the resonators and which are controlled by the application of an analog voltage.
Such a device, if it has some merit, however, requires a complex control and thus a sophisticated analog circuitry.
It is desirable to simplify the design of the command of the adjustment of acoustic resonators used in filtering circuits to allow, in particular, a more sophisticated command while being less costly to implement.